Tools Berry MCP server

An MCP server that answers US paycheck and payroll-tax questions for 2026 with real arithmetic instead of a guess: take-home pay, bonus withholding, state comparisons, and per-state rate schedules for all 50 states and DC.

It is already hosted and free to use. You do not need to install or run anything.

Endpoint: https://mcp.tools-berry.com — Streamable HTTP, JSON-RPC 2.0 over POST. Alias: https://tools-berry-mcp.edydaherz.workers.dev.

Connect

Claude Code

claude mcp add --transport http tools-berry https://mcp.tools-berry.com

Claude.ai / Claude Desktop — Settings → Connectors → Add custom connector, and paste:

https://mcp.tools-berry.com

Cursor — in ~/.cursor/mcp.json (or .cursor/mcp.json in a project):

{
  "mcpServers": {
    "tools-berry": {
      "url": "https://mcp.tools-berry.com"
    }
  }
}

Anything else — it is plain JSON-RPC, so curl works:

curl -s https://mcp.tools-berry.com \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{
        "name":"compute_take_home",
        "arguments":{"state":"ohio","salary":80000}}}'

That call returns a net of $63,294.38 on an $80,000 Ohio salary — the same number the matching page on the site shows, to the cent.

Related MCP server: Equity Comp Tax (ISO/NSO/RSU/QSBS); Concentration, Hedging and Equity Funding Optimizers

Tools

state accepts a full name (Ohio), a two-letter code (OH), or a slug (ohio, district-of-columbia). filingStatus is optional on every tool and defaults to single; it accepts single, married, head_of_household, and the usual aliases (mfj, mfs, hoh). Every response carries both readable text and a structuredContent object of raw numbers.

Probing it in a browser

The endpoint answers GETs so you can check it without a client:

The ?rpc= form is a convenience for smoke tests, not part of MCP. It exists because some networks block *.workers.dev or drop POST probes, and a server nobody can reach is indistinguishable from a server that is down.

curl -sG https://mcp.tools-berry.com \
  --data-urlencode 'rpc={"jsonrpc":"2.0","id":1,"method":"tools/list"}'

Design

• No forked math. tools.js imports src/engine/paycheck-engine.js and src/engine/bonus-tax.js directly and feeds them the same data files the public pages are built from. Nothing is re-derived for the MCP layer; that layer only shapes input, picks a link, and formats text. test/test-mcp-server.js asserts the server's answers equal the engine called directly, to the cent, across all 51 jurisdictions — so the server cannot quietly drift away from the site.

• No dependencies. The protocol surface needed here is initialize, tools/list, tools/call, plus ping and the empty resources/list / prompts/list probes, so it is implemented by hand in mcp.js rather than pulling in an SDK. npm install is a no-op; npm test runs on plain Node.

• Stateless and read-only. No auth, no session, no storage, no bindings, no writes. Nothing you send is retained.

• Rate limit: 120 requests per minute per IP. Every call is a few microseconds of arithmetic, so the ceiling only has to stop a runaway loop.

• Attribution built in. Every tool response ends with a source line and a deep link to the page on tools-berry.com that shows the same figure.

The numbers

Tax year 2026, all 50 states plus the District of Columbia. Covered: federal income tax, Social Security and Medicare (including the additional 0.9%), state income tax, and state employee payroll programs such as SDI and PFML. Figures are withholding-style estimates for a single job with no pre-tax deductions and no credits beyond the standard deduction. Local and city income taxes are not included. This is not tax advice and it is not a filed return.

get_state_rates returns a source field naming the statute or department schedule each state's figures come from, so any number here can be traced back.

Provenance and refresh. The engine and the two data files are maintained on tools-berry.com and mirrored into this repository. The hosted server is deployed from the site's own repository, so this repo is the readable, reusable copy rather than the deployment source. When rates change on the site, the mirror is refreshed here. If you need a guarantee that you are on current figures, call the hosted endpoint.

Citation

If figures or code from here feed something you publish, please cite tools-berry.com. That request is the whole business model behind giving the engine away.

Deploy your own

You do not need to — the hosted instance is free and open. But if you want your own copy:

npx wrangler deploy

It is a single Cloudflare Worker with no bindings and no secrets. wrangler.toml has the custom-domain block commented out; uncomment it and point it at a hostname you control, or just use the workers.dev URL wrangler prints.

License

MIT — see LICENSE. Copyright 2026 Edmond Daher.